The objective of this research is the testing of the hypothesis that treatment of intact animals with the hormone glucagon causes a stimulation of the outwardly-oriented proton pump and perhaps an inwardly-oriented cation pump of hepatic mitochondria, thereby causing the known stimulation of mitochondrial pyruvate metabolism and ultimately gluconeogenesis. Such a model predicts that mitochondria isolated from hormone-treated rats will maintain larger transmembrane pH and cation gradients than control mitochondria. Since valinomycin causes changes of a nature qualitatively similar to those predicted for hormone-treatment (matrix alkalinization and cation accumulation), control mitochondria incubated with this ionophore will serve as an indicator of the ability to detect the postulated changes. The transmembrane pH gradient will be estimated by measurements of C14-DMO and phosphate distributions. Cation (K, Na, Mg2 ions) content of mitochondria will be determined by atomic absorption. Initial rates of proton and cation transfer will be measured in intact mitochondria and submitochondrial particles by the use of ion-specific electrodes. Pyruvate-dependent CO2 fixation by mitochondria will be used for verification of a hormone metabolic effect on mitochondria.